Conventionally, display devices such as televisions, computer monitors, etc. receive and process an input of desired information through a processing unit, which is embedded therein or connected thereto, via a button or a mouse directly connected to the computer or the monitor.
In recent years, a variety of primary or assistant input techniques have been newly developed to substitute such a conventional input technique, and a touch screen type technique is one of such newly developed useful input techniques.
In the touch screen type technique, a display screen is provided with a resistance film or an ultrasonic wave generating means. Thus, when a user touches the screen with a finger or other input devices, there is variation in resistance or generation of surface acoustic wave on the screen, which is used to detect coordinates at a point on the screen touched by the user so as to input information and execute instructions thereby.
When using such a touch screen type input device, it is advantageous in inputting desired information with convenience.
However, with recent size-increasing trends of the display device employing such an input device, a distance between a user and the display device increases to an extent over the length of the user's arm, thereby providing a more frequent inconvenience of causing the user to move when touching the surface of the screen, as compared with a conventional condition where the user can touch the display device merely by stretching out their arm.
Further, a contact-type coordinate input system such as the touch screen type input system tends to experience not only screen contamination resulting from contact, but also deterioration in durability of a display panel resulting from repetitious application of load to the screen.
A non-contact type coordinate input system is developed to solve such problems. Unlike the contact type coordinate input system, the non-contact type coordinate input system does not require a physical contact between input means (finger, pen, etc.) and the screen. Instead, it employs other types of input means and detection means (sensor).
Specifically, the non-contact type coordinate input system typically uses light for inputting coordinates in such a way that light is illuminated to a desired location of the screen, and a coordinate set of the location is inputted to the display device, thereby performing the same function as that of the touch screen type input system. Although laser beam is generally used as light for this purpose, light is not specifically limited to the laser beam. Instead, the term “light” is used herein as a concept including electromagnetic waves in all ranges, such as infrared rays, ultraviolet rays, etc.
One example of the non-contact type coordinate input system is a photo-based direct pointing system disclosed in Korean Patent Laid-open Publication No. 2001-0026856. This system is conceived to achieve easy selection of a desired menu by direct pointing without troublesome manipulation of a remote controller. The system includes a pointer to select a menu by emitting light such as laser beam in a target direction, a detection unit having a light detection pad attached to the surface of the screen to detect a location on the screen where light emitted from the pointer enters, a location calculating unit to calculate the location on the screen based on a detection signal from the detection unit, a central processing unit (CPU) to control a cursor to be displayed on a calculated location and to control an associated operation of a menu corresponding to a location of the cursor to be performed by operation of a selection switch of the pointer, and a cursor generating unit to generate and display the cursor under control of the CPU.
Such a direct pointing system has merits in that a user does not require troublesome operation of the remote controller and can easily select a menu displayed on the screen by directly pointing at the menu with light.
Another example of the non-contact type coordinate input system is an input-output device disclosed in Japanese Patent Laid-open Publication No. H11-119910.
The input-output device of this disclosure detects a certain location on a display screen of the input-output device, and allows input of data corresponding to the detected location to be performed in a non-contact type manner. Specifically, the input-output device operates the certain location to detect the location on the display screen, and performs input and output corresponding to the detected location. In the input-output device, the certain location on the display screen is illuminated with light from a write pen for input of light. Then, one of plural photoelectric conversion elements provided integral with the display unit and arranged in a matrix receives the light at the light irradiated location, so the location corresponding to an output state of the photoelectric conversion element is detected.
Such an input-output device is also a useful device for inputting information to the screen in a non-contact type manner.
As can be appreciated from FIGS. 1 and 2, the techniques disclosed in Korean Patent Laid-open Publication No. 2001-0026856 and Japanese Patent Laid-open Publication No. H11-119910 adopt a method of inputting coordinates based on information obtained when light from the pointer and the like reaches respective sensors for detecting light, which are located at lattice points (for example, 1aa in FIG. 2a) corresponding to the respective coordinates.
However, such a coordinate input method may have problems when applied to large display devices or in the case of requiring more detailed classification of input coordinates. In other words, since the above coordinate input method requires the sensors such as optical sensors corresponding to the respective coordinates, it is necessary to provide a number of sensors corresponding to the number of coordinates for input. Further, when the sensors are arranged at constant intervals, the screen of the display device increases in size, so that the number of sensors for the display device also increases in proportion to a square value of an increased size (width or length) of the screen, thereby making it further difficult to arrange the sensors in the enlarged input device in practice.
Therefore, when making the display device large, such a great number of sensors can become a great burden to a manufacturer. This problem also occurs in the case of classifying the coordinates in more detail. When resolution of the coordinates increases, it is necessary to provide additional sensors so as to correspond to an increasing amount of resolution, and the number of sensors also increases in proportion to a square value of the resolution of the coordinates.
Further, when the sensors are provided to the respective coordinates, it is necessary to set some region as a sensor section 1aa and other regions as a pixel region 1ba independent of the sensor section 1aa, as shown in FIG. 2. Thus, to secure a sufficient surface area for the pixel region, the sensor must have a very small size, and, if not, deterioration in image quality inevitably occurs.